全文获取类型
收费全文 | 1484篇 |
免费 | 33篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 50篇 |
综合类 | 1篇 |
化学工业 | 383篇 |
金属工艺 | 23篇 |
机械仪表 | 25篇 |
建筑科学 | 61篇 |
矿业工程 | 9篇 |
能源动力 | 26篇 |
轻工业 | 183篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 92篇 |
一般工业技术 | 227篇 |
冶金工业 | 274篇 |
原子能技术 | 11篇 |
自动化技术 | 144篇 |
出版年
2022年 | 21篇 |
2021年 | 22篇 |
2019年 | 14篇 |
2018年 | 15篇 |
2017年 | 17篇 |
2016年 | 16篇 |
2015年 | 21篇 |
2014年 | 14篇 |
2013年 | 59篇 |
2012年 | 36篇 |
2011年 | 59篇 |
2010年 | 37篇 |
2009年 | 39篇 |
2008年 | 58篇 |
2007年 | 30篇 |
2006年 | 29篇 |
2005年 | 29篇 |
2004年 | 23篇 |
2003年 | 32篇 |
2002年 | 21篇 |
2001年 | 37篇 |
2000年 | 30篇 |
1999年 | 19篇 |
1998年 | 76篇 |
1997年 | 52篇 |
1996年 | 42篇 |
1995年 | 30篇 |
1994年 | 35篇 |
1993年 | 24篇 |
1992年 | 29篇 |
1991年 | 18篇 |
1989年 | 17篇 |
1988年 | 23篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 32篇 |
1976年 | 38篇 |
1974年 | 24篇 |
1973年 | 18篇 |
1972年 | 17篇 |
1971年 | 14篇 |
1967年 | 12篇 |
排序方式: 共有1518条查询结果,搜索用时 15 毫秒
71.
Safren Steven A.; O'Cleirigh Conall; Tan Judy Y.; Raminani Sudha R.; Reilly Laura C.; Otto Michael W.; Mayer Kenneth H. 《Canadian Metallurgical Quarterly》2009,28(1):1
Objective: To evaluate cognitive-behavioral therapy to enhance medication adherence and reduce depression (CBT-AD) in individuals with HIV. Design: A two arm, randomized, controlled, cross-over trial comparing CBT-AD to enhanced treatment as usual only (ETAU). ETAU, which both groups received, included a single-session intervention for adherence and a letter to the patient's provider documenting her or his continued depression. The intervention group also received 10 to 12 sessions of CBT-AD. Main Outcome Measures: Adherence to antiretroviral therapy as assessed by Medication Event Monitoring Systems (MEMs) and depression as assessed by blinded structured evaluation. Results: At the acute outcome assessment (3-months), those who received CBT-AD evidenced significantly greater improvements in medication adherence and depression relative to the comparison group. Those who were originally assigned to the comparison group who chose to cross over to CBT-AD showed similar improvements in both depression and adherence outcomes. Treatment gains for those in the intervention group were generally maintained at 6- and 12-month follow-up assessments. By the end of the follow-up period, those originally assigned CBT-AD demonstrated improvements in plasma HIV RNA concentrations, though these differences did not emerge before the cross-over, and hence there were not between-groups differences. Conclusions: CBT-AD is a potentially efficacious approach for individuals with HIV struggling with depression and adherence. Replication and extension in larger efficacy trials are needed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
72.
DI Marlene Haimann ao.Univ.-Prof. i. R. Dr. Otto Moog DI Dr. Ilse Stubauer Priv.-Doz. DI Dr. Michael Tritthart Univ.-Prof. DI Dr. Helmut Habersack 《?sterreichische Wasser- und Abfallwirtschaft》2014,66(9-10):316-326
In the case study “Winterhafen Linz” the effects of dredging/excavating fine sediments previously deposited by flood events and their subsequent dumping into the Danube mainstream were investigated. While this maintenance work was in progress, the temporal and spatial extent of the sediment plume and the changes in bed topography were measured. By employing air-lift samplers and grab samplers in the dredging and dumping areas, the question as to whether, and if so to what extent, the benthic invertebrate community was disturbed by the maintenance work. It could be clearly demonstrated that the sediment dredging severely affected the benthic invertebrates (an 82 % decline in biomass), while the dumping of the material had no effects on the Danube biota. Numerical modeling was used to simulate discharges and dumping locations other than those actually encountered during the monitoring campaign, thus making it possible to extrapolate and draw conclusions beyond the concrete results. These findings in turn provided the basis for recommendations on how to optimize dredging and dumping procedures on the Danube in future. 相似文献
73.
Andreas Opitz Bernhard Ecker Julia Wagner Alexander Hinderhofer Frank Schreiber Jochen Manara Jens Pflaum Wolfgang Brütting 《Organic Electronics》2009,10(7):1259-1267
Blends of organic electron and hole conductive materials are widely used for ambipolar charge carrier transport and photovoltaic cells. An obvious choice for donor–acceptor blends are organic semiconducting materials in their hydrogenated and fluorinated form, since they combine potentially suitable electronic properties with structural compatibility of the two constituents. This study focuses on the structural, optical, and electrical properties of blends using hydrogenated copper-phthalocyanine (H16CuPc) in combination with its per-fluorinated version (F16CuPc). Using X-ray scattering, scanning force microscopy and optical absorption measurements we show that mixed crystalline films are obtained by co-evaporation of the two materials. Electrical transport measurements reveal a profound reduction of the current for bipolar charge injection in mixed films. We discuss the formation of self-trapped charge transfer excitons as possible explanation for this unexpected behaviour, which impedes the usability of this system in photovoltaic cells. 相似文献
74.
The time evolution of the density operator of an AB spin system during a double-spin-echo pulse sequence is evaluated analytically by a computer-algebra system. The computer-algebra system allows one to generate the extensive formulas describing the density operator and yields an expression for the integral of the spectral signals. The simulation of spectra for arbitrary sequence timings can be easily performed by this new tool without risking errors that might occur in conventional calculations. The computer-algebra method can be extended straightforward to other pulse angles and types of sequences. The double-spin-echo pulse sequence is used in the point-resolved spectroscopy (PRESS) method which is often applied for volume selective examinationsin vivo. For verification of the results generated by the computer-algebra system,1H spectra from a half-liter spherical sample with an aqueous solution that was 0.1 M in sodium citrate and 0.1 M in sodium acetate were recorded after 90°-180°-180° double-spin-echo pulse sequences on a 1.5-T whole-body unit. The measured behavior of the citrate AB spin system corresponds very well with the theoretical predictions. Thus, the theory provides the basis for the optimization of sequence timings for double-spin-echo measurements with high signal gain from AB systems as, for example, citrate. In addition, the theoretically predicted signal modulations could be fitted to the experimental data, providing the transverse relaxation time of the AB-coupled protons. 相似文献
75.
Bernd Trummer Otto Fruhwirth Klaus Reichmann Gerhard Herzog Werner Sitte Michael Holzinger 《Journal of Electroceramics》2000,5(1):53-61
Conductive LaNiO3 thin film electrodes were deposited by chemical solution deposition (CSD) from nitrate solutions onto polycrystalline Al2O3 and (Ba,Ca)TiO3 PTCR ceramic substrates. The electrical properties of the LaNiO3 thin film on Al2O3 and of the interface consisting of LaNiO3 and the semiconductive oxide ceramic were investigated. The deposited LaNiO3 films were about 250 nm thick and consisted of nanosized particles. The resistivity of the LaNiO3 film was about 3 × 10-3cm at 20°C. The PTCR ceramic consisted of m sized particles and exhibited an electronic resistivity of about 10 cm at 20°C and a steep increase of the resistivity of a few orders of magnitude above the Curie point at about 120°C. The electrical properties of the LaNiO3/PTCR interface were dominated by the properties of a barrier layer between the PTCR ceramic and the LaNiO3 electrode. The potential dependence of the impedance indicated that the barrier layer consisted of a depletion layer within the PTCR ceramic, when the flat band potential of LaNiO3 on the PTCR ceramic at about –250 mV was exceeded. Additionally the formation of an insulating layer at the LaNiO3 electrode has to be taken into account. 相似文献
76.
77.
The cortical actin cytoskeleton undergoes dramatic rearrangements during fertilization of sea urchin eggs. To characterize these changes further, we quantified the relative changes in filamentous actin (F-actin) during fertilization and the first cell cycle in both intact eggs and in isolated cortices by quantitative fluorescence microscopy. The level of F-actin in the intact egg decreased after fertilization and continued to decrease throughout the first cell cycle. By 60 min after fertilization, the level of F-actin had decreased to 50% of the unfertilized sea urchin egg. By cytokinesis, the level of F-actin had decreased to 30% of the unfertilized egg. After completion of cell division, individual blastomeres had 10% of the F-actin in the unfertilized egg. In contrast, there was an increase in cortical F-actin to 370% of the level in the unfertilized egg after fertilization. This increase corresponded to the formation of microvilli. There was little change in the level of cortical F-actin during the first cell cycle. We draw parallels to other systems that increase the amount of F-actin in the Triton-insoluble cytoskeleton by recruiting actin from a Triton-soluble pool of F-actin. 相似文献
78.
79.
Kh Otto 《Canadian Metallurgical Quarterly》1996,(3):34-41
To make a diagnosis and a differential diagnosis of mediastinal tumors always encounters many difficulties. Differentially, the diagnostic spectrum includes a great number of histologically different tumor types. Routine light microscopic techniques are frequently insufficient for a tumor to be classified. This mainly applies to thymomas and malignant lymphomas. So tumor morphological diagnostic techniques have been improved year after year. Immunohistological techniques may further serve as a method of precision diagnosis of tumors. The application of these methods largely changes our logic and implies a close cooperation between diagnosis and therapy. 相似文献
80.
A review of the synthesis and characterization of a new type of stacked, bridged macrocyclic metal complexes, the (μ-cyano)phthalocyaninatometal compounds [PcMCN]n (2) is given. By using the routes described in Fig. 3 the polymers were synthesized with M = Co3+, Fe2+, Fe3+, Mn3+ and Cr3+ as the central metal ion. The compounds were characterized by IR, far-IR, UV, thermal and elemental analysis, and partly by 1H NMR and FD (field desorption) mass spectroscopy.[PcCoCN] (2a) and [PcFeCN]n (2b) exhibit d.c. room temperature conductivities around 10?2 S/cm without doping, thereby showing conductivities which are in the same range as the iodine-doped phthalocyaninatosiloxanes [PcSiO]n. 相似文献